1. Field of the Invention
The present invention relates generally to an image capture device of a camera, and more particularly to an optical image stabilizer of a camera.
2. Description of the Related Art
As shown in FIG. 1 and FIG. 2, a conventional optical image stabilizer 3, which is provided in a camera at an image side of a lens to assist an image capture device 4 (CCD or CMOS), includes:
A base 50 is mounted in the camera and has a pair of transverse rails 51.
A pair of transverse reference magnets 60a and a pair of longitudinal reference magnets 60b are mounted on the base 50.
A transverse frame 70a is mounted on the transverse rails 51 for reciprocation. The transverse frame 70a is provided with a pair of longitudinal rails 71, on which a longitudinal frame 70b is mounted for reciprocation. The image capture device 4 is mounted on the longitudinal frame 70b that the image capture device 4 may move along the longitudinal rails 71.
A transverse drive coil 80a and a longitudinal drive coil 80b are mounted on the longitudinal frame 70b and are in association with the transverse reference magnets 60a and the longitudinal reference magnets 60b are respectively. The transverse drive coil 80a and the longitudinal drive coil 80b may move the longitudinal frame 70b when a power supplies to the transverse drive coil 80a and the longitudinal drive coil 80b that the longitudinal frame 70b may move in a vertical direction and in a horizontal direction according to the currents supplying to the transverse drive coil 80a and the longitudinal drive coil 80b. 
As shown in FIG. 3, when user operate the camera equipped with the optical image stabilizer 3, it will provide the transverse drive coil 80a and the longitudinal drive coil 80b predetermined currents when the camera detects shake, vibration, or tilt that the transverse drive coil 80a and the longitudinal drive coil 80b may generate magnetic fields on the transverse reference magnets 60a and the longitudinal reference magnets 60b to move the longitudinal frame 70b, with the image capture device 4 thereon, in predetermined directions to reduce the shake.
In such optical image stabilizer 3, as shown in FIG. 4, the longitudinal drive coil 80b is outside the longitudinal rails 71 that the magnetic forces Fr or Fa between the longitudinal drive coil 80b and the longitudinal reference magnets 60b may generate a torque Rr or Ra on the longitudinal frame 70b. It is easy to understand that the longitudinal frame 70b is like a lever at this moment, wherein the longitudinal rail 71 (the fulcrum) proximal to the longitudinal drive coil 80b has the torque Rr or Ra, and the other longitudinal rail 71 has a load fr or fa. For the same principle, it will provide a torque fu on the longitudinal rail 71 when the longitudinal drive coil 80b generates a force Fu to move the longitudinal frame 70b in the longitudinal direction, as shown in FIG. 5.
The torques and the loads on the longitudinal rails 71 may hinder the longitudinal frame 70b from movement that reduces the sensibility of the optical image stabilizer 3 in reduction of shake.